This relates to testing integrated circuits, and more particularly, to testing integrated circuits with probe cards such as cantilever probe cards.
Integrated circuit manufacturing operations involve testing. Testing may be performed while integrated circuits are in wafer form or after individual die have been packaged.
Packaged die can be tested by placing the die in test sockets. Each test socket has a pattern of contacts that mate with the contacts on a die package. During testing, a test socket that contains a packaged die is connected to a tester. The tester applies power supply and data signals to circuitry on the die through the socket.
This type of arrangement works well for packaged die, but cannot be used with unpacked die because unpackaged die cannot interface with the contacts in the socket.
To enable testing of upackaged die, test systems use test probes. These probes, which are sometimes referred to as probe cards, have probe pins that mate with the exposed contacts on an unpackaged die. Die can be probed using test probes when still in wafer form or after dicing a wafer into individual die.
In a typical arrangement, a wafer of die to be tested is placed on a test stage. The test stage may include a vacuum chuck to hold the wafer in place. The distance between the probe card and the wafer is decreased until the probe pins in the probe card come into contact with mating pads on the surface of the die. A tester that is connected to the probe card can then test the circuitry on the die. Power signals can be applied to the pads of the die through the probe pins. Input test signals can be applied to the die through the probe pins and corresponding output test signals can be gathered through the probe pins.
Integrated circuit die whose pads have a sufficiently wide pitch may be probed using probe cards with vertical pins. Integrated circuit die with more finely spaced pads generally require the use of cantilever probe cards.
In a typical cantilever probe cards, probe pins are angled toward the surface of the die. Because of the way in which the probe pins are mounted within the probe card, the probe pins run parallel to each other and are in close proximity to one another. This type of layout for the probe pins cannot generally be avoided in a cantilever probe card. Unfortunately, at high signal speeds this type of layout can lead to undesired cross-talk due to inductive coupling between nearby pins. Cross-talk effects tend to be additive, so in the presence of numerous high-speed signals there is a significant potential for signal disruption in conventional cantilever probe cards.
It would therefore be desirable to be able to minimize cross-talk in cantilever probe cards and to provide improved test systems with minimized probe card cross-talk effects.